What is epilepsy? - Chapter 16

How is epilepsy defined?

Epilepsy is not a simple syndrome, but instead comprises a broad category of symptom complexes with various possible underlying brain function disorders, which cause sudden recurring episodes of electrical discharges. These are manifested as stereotypical behavioural changes, which are referred to as epileptic seizures. Some epilepsy patients also experience cognitive and behavioral disorders that can also be caused or enhanced by treatment with anti-epileptics or surgery.

What does the clinical picture look like?

Epilepsy is the most common chronic neurological disorder in which there is a continuous tendency to generate epileptic seizures and by its psychological, social, cognitive, and neurobiological consequences (Fisher and colleagues, 2005). One out of ten people will ever experience an epileptic seizure. The prevalence of epilepsy is highest before the age of ten years and after the age of 65 years. Depending on the location of the epileptic discharges, behavioral changes can occur within four categories:

1. Altered consciousness.

2. Involuntary movements.

3. Perceptual or autonomous changes.

4. Behavioral changes.

There are two types of classification systems that are both used in clinical practice: the seizure classification and the epilepsy syndrome classification. In the attack classification, only the attack phenomena are considered. In the epilepsy syndrome classification, the age of onset of the seizures, treatment options, and the prognosis play an important role.

How are epileptic seizures and epilepsy syndromes classified?

The first classification of epileptic seizures was made in 1970: a partial / focal attack would occur in a specific part of the brain while a generalised attack is caused by discharges throughout the brain. This dichotomy is still being used. The classification of seizures distinguishes subcategories within these categories. For example, a simple partial seizure is a seizure, without loss of consciousness: this is the case with a complex partial seizure. An absence, on the other hand, is a primarily generalized seizure that is mainly present in childhood. The core symptom, the absences (periods of consciousness loss), usually last ten seconds and the patient does not respond to anything in these ten seconds. Often the child does not even realize that he / she has experienced a seizure. A tonic-clonic seizure is the most common generalised attack in which the (adult) patient loses consciousness for a few minutes. It starts with a contraction of all muscles (tonic) and after about 30 seconds this changes into rhythmic contractions (clonic spasms). The seizure usually ends spontaneously after which the patient falls asleep or comes into a confused state. If the seizure is immediately followed by a subsequent attack, medical intervention is required. Other generalized attacks are myoclonic attacks, tonic attacks and clonic attacks.

Within the classification of epilepsy syndromes (1989) attention is also paid to the localisation and the cause of the seizure. Within this system, the partial epilepsy syndromes are also distinguished from the generalized epilepsy syndromes, but each category falls apart into an idiopathic, symptomatic, and cryptogenic type of epilepsy:

• Partial epilepsy

  • Idiopathic: no cause can be determined.

  • Symptomatic: the cause is known (for example a brain tumor).

  • Cryptogenic: there is a strong suspicion of a neurological cause based on the severity of the epilepsy, but for the time being at least it is impossible to establish this by means of a neurological examination. 

What is the pathophysiology of epileptic seizures?

It is still unclear whether the epileptic discharges are caused by a dysfunctional ion channel in the cell membrane or an imbalance in the neurotransmitters. Anti-epileptics inhibit the exciting effect (due to glutamate) or enhance the inhibiting effect (by stimulating GABA). Generalised seizures involve a diffuse lowering of the seizure threshold in the cortex. In the case of focal attacks, the cause can be found in congenital disorders (such as neurodegenerative disorders) or in TBI.

How is epilepsy treated?

Anti-epileptic drugs keep the attacks under control, but do not eliminate the cause of the epilepsy. It therefore depends on the subjective suffering of the patient whether to use medication or not. The type of epilepsy is also important, because some types of epilepsy will pass on their own. One of the most effective remedies for absence epilepsy is valproate (Depakine); Carbamazepine (Tegretol) is a remedy for partial seizures. It is preferable to use the medication as monotherapy, but if the first choice anti-epileptic medication does not work, it is possible to switch to polytherapy (the prescribing of two or more types of drugs). 65% of patients treated with anti-epileptics are seizure-free. The patient must be seizure-free for two to five years before stopping the anti-epileptic medication. The reduction must be done slowly. The patients who do not respond to the anti-epileptics are called 'refractory' patients. In some of these patients - those with focal epilepsy - a surgical procedure can be chosen. For example, in the case of temporal lobe epilepsy, the first few centimeters of the temporal lobe are removed: in 70% of the cases, the attacks disappear, while in other patients the attack frequency reduces. If a surgical procedure proves impossible, it is possible to choose for a 'vagus nerve stimulation' (VNS). This treatment is based on the assumption that attacks are caused by abnormal synchronization of neuronal firing. With an VNS, an extracranial stimulator (placed under the breast) is placed, which in turn causes 'desynchronisation'. Stimulating desynchronisation leads to a lower attack frequency (Majoie, Rijkers, Cornip & Berfelo, 2007). Recently a new method of treatment has been introduced: deep brain stimulation. By placing an electrode deep in the brain (in the thalamus) that fires occasionally, epileptic discharges are interrupted or even prevented. A somewhat controversial treatment is the ketogenic diet: patients must adhere to very strict guidelines and must eat a high-fat, low-protein, low-starch and low-sugar diet that causes the level of ketones to rise and occasionally have an anti-epileptic effect.

What are the neuropsychological consequences of epilepsy?

Ideopathic epilepsies

Compared to symptomatic epilepsy, ideopathic epilepsies are associated with less severe neuropsychological disorders, and are easier to treat. Verbal memory and language seem to be relatively intact, while information processing is not. In the long term the most frequently heard complaint - the slow speed of information processing - will interfere with daily activities in such a way that intellectual decline occurs. In general, there are relatively mild neuropsychological consequences that are caused by active attacks within a functional domain during a critical development period. Sometimes there is cognitive recovery; sometimes subtle residual symptoms remain.

Symptomatic epilepsies

Nearly three-quarters of patients with symptomatic epilepsy suffer from temporal lobe epilepsy (TLE). In a TLE, primarily memory disorders occur. Mesiotemproal anomalies often involve impairments of the consolidation and retrieval of verbal episodic information, whereas neocortical anomalies result in impairments in remembering verbal semantic content related to language. Specific memory disorders are the result of left (mesio) temporal damage. On the other hand, relating non-verbal memory functions to right hemisphere damage is less specific. In 20% of patients, the second most common symptomatic epilepsy is the frontal lobe epilepsy (FLE). In this epilepsy, the same structural abnormalities are present to a lesser extent, resulting in more diffuse neuropsychological consequences (especially within the executive domain). There are no reported specific profiles for patients with parietal lobe epilepsy or occipital lobe epilepsy.

The side effects of anti-epileptic drugs

The choice for an anti-epileptic drug is not only based on the type of epilepsy but also on experience. The treatment is changed a lot, depending on the complaints that the patient experiences. The side effects are so serious that the quality of life is strongly influenced. The drug increases postsynaptic inhibition and decreases the excitation of the cell membrane. Polytherapy is often more effective than monotherapy. In their article, Aldenkamp and colleagues (2008) describe the specific side effects of all types of anti-epileptic drugs. The book only concludes that for most drugs there are mild to severe side effects, with particular attention to memory disorders and mental slowness.

Psychiatric disorders in patients with epilepsy

Psychiatric disorders are more common in epilepsy patients than in healthy controls. Due to the involvement of the limbic system and the sensitivity of the temporal brain structures to seizures, the most common psychiatric disorders in epilepsy patients are anxiety disorders, depression, personality changes and psychoses. Approximately 50% of epilepsy patients suffer from an anxiety disorder or depression. Because of the unpredictability and uncontrollability of the attacks, anxiety symptoms quickly arise. A depressed mood often occurs just before an attack, so that it cannot only be a consequence but also a symptom of the attack. Depression is most evident during a (focal) attack. Eventually, depression can be a side effect of anti-epileptic drugs. 30% of TLE and FLE patients have a personality disorder (dependent disorder, avoidant disorder, or obsessive-compulsive disorder). Psychoses are more common after an attack (in 25% of the cases) than during an attack (in this case they are more severe and longer lasting and are often related to an epileptic state.

The psychosocial consequences of epilepsy

Epilepsy patients experience more psychosocial problems than healthy controls mainly due to the unpredictability of their attacks. Other contributing factors are low self-esteem, low social support, a negative attitude towards epilepsy patients, and lower expectations of their own cognitive performance.